The rapid dissolution of plutonium dioxide by a sodium peroxide-sodium hydroxide fusion, followed by determination of the plutonium content by controlled-potential coulometry

Abstract

A method is described for the dissolution of plutonium dioxide, followed by determination of the plutonium content by controlled-potential coulometry. The plutonium dioxide is brought into solution by fusion with a mixture of sodium peroxide and sodium hydroxide at 600° C for 15 minutes in an alumina crucible. The cold melt is leached with water, which is then acidified with sulphuric acid. The solution is heated for 15 minutes to decompose hydrogen peroxide and, after cooling, diluted to a suitable volume. The plutonium content of an aliquot containing about 4 mg of plutonium is determined by controlled-potential coulometry. A potential of + 0·30 volt versus a S.C.E. is used for reduction to plutonium(III), whereas + 0·70 volt versus a S.C.E. is used for the quantitative oxidation to the plutonium(IV) state.

Mean recoveries on 100-mg amounts of plutonium dioxide that had been ignited at 850° C were 99·95 per cent., with a coefficient of variation of 0·11 per cent. For the complete dissolution of samples previously ignited at higher temperatures (about 1600° C), an increase in the ratio of the weight of fusion mixture to sample is necessary. Mean recoveries on 50-mg amounts of plutonium dioxide that had been ignited at 1600° C were 99·85 per cent., with a coefficient of variation of 0·54 per cent.